This proposal is for continuation of our ongoing research on opioid abnormalities and blood pressure reactivity in persons at risk for hypertension. We are gradually becoming aware that regulation of both blood pressure and pain sensitivity is altered in pre-hypertensive populations. For example, persons at risk for hypertension have decreased opioid inhibition of blood pressure responses to stress. Paradoxically, they also show antinociceptive effects consistent with exaggerated opioid function. The scientific meaningfulness, both basic and clinical, of the links between pain sensitivity alterations and blood pressure dysregulation remains to be clarified. Recent studies by ourselves and others have emphasized the importance of opioids in regulation of 1) neuroendocrine and blood pressure responses to stress in hypertension development, 2) behavioral responses to pain, and 3) the relationship between pain sensitivity and blood pressure. The purpose of this continuation proposal is to further examine the role of endogenous opioids in blood pressure dysregulation by studies of circulatory and behavioral responses to aversive stimuli in persons at enhanced risk for hypertension. This will be accomplished by comparison of the effects of opioid blockade with naltrexone on pain sensitivity and blood pressure reactivity in young men and women with mildly elevated casual blood pressure. We hypothesize that abnormalities of both blood pressure control and pain sensitivity in the early stages of hypertension development are linked to altered opioid peptide function. Persons at risk for hypertension will show exaggerated opioid inhibition of pain sensitivity in the face of diminished opioid inhibition of blood pressure reactivity. Improved understanding of the opioidergic basis of altered pain sensitivity and blood pressure control will clarify the poorly characterized etiology of essential hypertension and possibly offer new preventive, diagnostic and therapeutic strategies.